This invention relates to the rolling of a metal strip such as aluminum strip in a rolling mill stand and to a means for preventing a substantial amount of liquid applied to the rolls from entering into a gap in a non-rolling area of the work rolls while the strip is being rolled, and the removal of any liquid finding its way to the delivery side which may be through the non-rolling area.
In the cold rolling of metal strip, such as aluminum, liquid lubricant or coolant is applied to the work rolls and to the strip for a number of reasons, some of which are: to reduce the wear of the work rolls; to improve the surface quality of the strip; to reduce frictional heat generated during the rolling process, etc. The coolant applied to the work rolls lands onto the top and bottom surfaces of the strip. Usually this coolant or lubricant is an oil-in-water emulsion. If this water base liquid remains on the surface of the strip for any length of time it has a tendency to stain or mar the strip, which condition is undesirable for many commercial purposes.
Therefore, as disclosed in U.S. Pat. No. 3,192,752 wherein upon the strip's exiting from a four stand continuous four-high mill and prior to the coiling of the strip, a means and method has been devised to remove as much lubricant as possible from the strip's surfaces. This is done by arranging a plurality of air jets above and below the strip and directing these jets onto the strip and adjacent the work rolls on both sides of the strip in a manner to blow the rolling lubricant and any free water off the sides of the strip toward the sides of the mill where an exhaust system collects and withdraws the air as well as the emulsion and water. Further on down the mill line and still prior to the recoiling of the strip, again air is applied to the top and bottom of the strip while an exhaust system removes the liquid emulsion.
Several disadvantages and problems arise from the design disclosed in the '752 patent which the present invention at least substantially resolves. One of the limitations of the '752 design is that on the delivery end of the mill a considerable amount of liquid remains on the strip after it has passed beyond the air jets.
It was concluded that this condition was due to the following:
As is known in the rolling process, coolant is applied to the work rolls prior to the strip's entry into a stand of the mill. Since the coolant cannot pass between the rolls in the area engaging the strip there is a tendency to create a puddle or a buildup on top of the strip immediately adjacent the roll bite on the entry side. Some of this buildup of liquid runs off on both sides of the strip and finds its way onto the delivery side of the stand. One way in which this happens is that the liquid passes through the rolls in the open space of the roll gap extending from the edges of the strip outwardly toward the roll necks. The rotation of the rolls results in the coolant being thrown into the air and landing on the strip downstream of the air jet system of the '752 patent. Therefore, a considerable amount of liquid is on the strip even after the strip has passed through the air jet area.
In essence, the air jet system of the '752 patent does not remove most of the liquid off of the strip when it is most advantageous to do so.